A communication system may be seen as a facility that enables communication sessions between two or more nodes such as fixed or mobile communication devices, access points such as nodes, base stations, servers, hosts, machine type servers, routers, and so on. A communication system and compatible communicating devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols may define the manner how communication devices shall communicate with the access points, how various aspects of the communications shall be implemented and how the devices and functionalities thereof shall be configured.
An example of cellular communication systems is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) or long-term evolution advanced (LTE advanced) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. In LTE base stations providing the cells are commonly referred to as enhanced NodeBs (eNB). An eNB may provide coverage for an entire cell or similar radio service area.
A user may access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user device (UE), user device or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. In wireless systems a communication device typically provides a transceiver station that may communicate with another communication device such as e.g. a base station. A communication device such as a user device (UE) may access a carrier provided by a base station, and transmit and/or receive on the carrier.
Capacity of a communication system may be improved by providing network densification—increasing a number of network nodes and decreasing an average distance between user equipment and network nodes. One method of increasing densification of a network is to provide smaller nodes (for example low power nodes) under the control of more powerful macro nodes. The smaller nodes may provide the network with an increased traffic capacity while the macro nodes may provide service availability for the coverage area.
In dual connectivity, a user equipment is connected to both a master node and a secondary node at the same time. An example of this is a system with both macro nodes and small nodes deployed, and a dual connectivity UE may carry out simultaneous (dual) communication with a macro node and a small node. The functionality of the macro and small nodes may be arranged in different ways, for example control signaling may be carried out through the macro node while data signaling may be carried out through the small node and/or uplink and downlink connectivity may be separated between the macro and small node and/or part of the data signaling may be carried out through the small node to achieve offloading of the macro node
Connection re-establishment is carried out for a user equipment when a connection to serving node has failed, for example in the case of a failed handover and/or due to a radio link failure in serving node. In connection re-establishment, a link between a user equipment and serving node is re-established and then reconfiguration may be carried out to re-establish the radio bearers for the communication.
In the case of dual connectivity network this re-establishment may become more complicated. Embodiments of the present application aim to address the re-establishment procedure in dual connectivity networks.
According to a first aspect, there is provided a method comprising: providing a primary cell by a first node for a user equipment operating in dual-connectivity with the first node and a second node; and configuring the user equipment to send a request to a primary secondary cell provided by the second node requesting that the primary secondary cell provide the functionality of the primary cell for the user equipment when a radio link between the user equipment and the primary cell is lost.
Alternatively, the first aspect may comprise a method comprising: providing a primary cell by a first node for a user equipment operating in dual-connectivity with the first node and a second node; and configuring the second node to provide the functionality of the primary node in response to a request from the user equipment when a radio link between the user equipment and the primary cell is lost.
The second node may be configured by the first node providing a user context to the second node. The user context may for example be provided during a dual connectivity set up procedure.
The method may further comprise providing a user equipment context to the primary secondary cell. The user equipment context may comprise information relating to carrying out the functionality of a primary cell. The functionality of the primary cell may comprise providing a radio resource control connection for the user equipment. The user equipment context may comprise information relating to providing a radio resource control connection. The user equipment context may comprise radio resource control connection parameters for the user equipment.
The method may further comprise providing a user equipment context to the primary secondary cell during a dual connectivity setup procedure. Configuring the user equipment may further comprise configuring the user equipment during a dual connectivity configuration procedure. The method may further comprise receiving a request from the primary secondary cell to release the primary cell for the user equipment. The method may further comprise releasing a primary cell for the user equipment in response to the release message.
The user equipment may be in dual connectivity with a master access node and a secondary access node, wherein the master access node provides the primary cell for the UE and the secondary access node provides the primary secondary cell for the UE.
According to a second aspect, there is provided a network access node comprising at least one processor and a memory, the at least one processor and memory configured to: provide a primary cell for a user equipment operating in dual connectivity with the network access node and a second node; and configure the user equipment to send a request to a primary secondary cell provided by the second node requesting that the primary secondary cell provide the functionality of the primary cell for the user equipment when a radio link between the user equipment and the primary cell is lost
The network access node may be a master network access node.
The network access node may be further configured to provide a user equipment context to the primary secondary cell. The network access node may be further configured to provide a user equipment context to the primary secondary cell during a dual connectivity setup procedure.
Configuring the user equipment may further comprise configuring the user equipment during a dual connectivity configuration procedure. The network access node may be further configured to receive a request from the primary secondary cell to release the primary cell for the user equipment. The network access node may be further configured to release a primary cell for the user equipment in response to the release message.
According to a third aspect, there is provided a method comprising: providing a primary secondary cell by a second node for a user equipment operating in dual connectivity with a first node and the second node; and receiving a request from the user equipment requesting that the primary secondary cell provide the functionality of a primary cell for the user equipment when a radio link between the user equipment and a primary cell provided by the first node is lost.
The method may further comprise providing the functionality of the primary cell for the user equipment in response to the request. The method may further comprise receiving a user equipment context from the primary cell. The user equipment context may comprise information relating to carrying out the functionality of a primary cell. The functionality of the primary cell may comprise providing a radio resource control connection for the user equipment. The user equipment context may comprise information relating to providing a radio resource control connection. The user equipment context may comprise radio resource control connection parameters for the user equipment.
The method may further comprise receiving a user equipment context from the primary secondary cell during a dual connectivity setup procedure. The method may further comprise determining that the request from the user equipment corresponds to a user equipment context received from the primary cell. The method may further comprise generating dual connectivity configuration information for the user equipment.
According to a fourth aspect, there may be provided a network access node comprising at least one processor and a memory, the at least one processor and memory configured to: provide a primary secondary cell for a user equipment operating in dual connectivity with a first node and the network access node; and receive a request from the user equipment requesting that the primary secondary cell provide the functionality of a primary cell for the user equipment when a radio link between the user equipment and the primary cell provided by the first node is lost.
The network access node may be a secondary network access node. The network access node may be further configured to provide the functionality of the primary cell for the user equipment in response to the request. The network access node may be further configured to receive a user equipment context from the primary cell. The network access node may be further configured to receive a user equipment context from the primary secondary cell during a dual connectivity setup procedure.
The network access node may be further configured to determine that the request from the user equipment corresponds to a user equipment context received from the primary cell. The network access node may be further configured to generate dual connectivity configuration information for the user equipment.
According to a fifth aspect, there is provided a method comprising: determining by a user equipment operating in dual connectivity with a primary cell provided by a first node and a primary secondary cell provided by a second node that a radio link with the primary cell is lost; and sending a request to the primary secondary cell requesting that the primary secondary cell provide the functionality of the primary cell for the user equipment.
The method may further comprise receiving a configuration message from the primary cell configuring the user equipment to send a request to a primary secondary cell requesting that the primary secondary cell provide the functionality of the primary cell for the user equipment when a radio link between the user equipment and the primary cell is lost.
The configuration message may be received during a dual connectivity configuration procedure. The method may further comprise receiving a response to the request from a secondary primary cell. The response to the request may comprise dual connectivity configuration information for the user equipment. The functionality of the primary cell may comprise providing a radio resource control connection for the user equipment.
The user equipment may be in dual connectivity with a master access node and a secondary access node, wherein the master access node provides the primary cell for the UE and the secondary access node provides the primary secondary cell for the UE.
According to a sixth aspect, there is provided an apparatus comprising at least one processor and a memory, the at least one processor and memory configured operating in dual connectivity with a primary cell provided by a first node and a primary secondary cell provided by a second node, the apparatus further configured to: determine that a radio link with the primary cell is lost; and send a request to the primary secondary cell requesting that the primary secondary cell provide the functionality of the primary cell for the user equipment.
The apparatus may be further configured to receive a configuration message from the primary cell configuring the user equipment to send a request to a primary secondary cell requesting that the primary secondary cell provide the functionality of the primary cell for the user equipment when a radio link between the user equipment and the primary cell is lost. The apparatus may be further configured to receive a response to the request from a secondary primary cell.
According to a seventh aspect, there is provided a system comprising: a primary cell provided by a first node; a primary secondary cell provided by a second node; and a user equipment in dual connectivity with the primary and primary secondary cells; wherein during a dual connectivity configuration of the user equipment, the user equipment is configured to send a request to a primary secondary cell requesting that the primary secondary cell provide the functionality of the primary cell for the user equipment when a radio link between the user equipment and the primary cell is lost.